The term “battery” originally referred to a plurality of galvanic cells connected in series. Today, however, individual galvanic cells (individual cells) are also frequently known as a battery. During the discharge of a galvanic cell, an energy-providing chemical reaction takes place, which is composed of two electrically mutually coupled, but spatially mutually separate, partial reactions. Electrons are released in an oxidation process at the negative electrode, resulting in an electron current, via an external load, to the positive electrode which receives a corresponding number of electrons. A reduction process therefore takes place at the positive electrode. At the same time, an ion current corresponding to the electrode reaction is established within the cell. This ion current is ensured by an ion conducting electrolyte. In secondary cells and batteries, this discharge reaction is reversible. It is, therefore, possible to reverse the conversion of chemical energy into electrical energy which has taken place during the discharge.
Among known secondary batteries, comparatively high energy densities are achieved in particular in lithium-ion batteries, i.e. in batteries in which lithium ions migrate from one electrode to the other during the charge and discharge processes. A lithium-ion battery comprises at least one individual cell having at least one positive and at least one negative electrode. In particular, it can comprise an individual cell in the form of a winding.
In many cases, the at least one individual cell of a lithium-ion battery is inserted into the interior of a prismatic metal housing. The metal housing is normally composed of a receptacle having a rectangular housing base and four side walls arranged at a right angle thereto and a housing cover that substantially has the same shape and size as the housing base. In other words, it is preferably cuboidal. The housing cover is generally barely profiled and can be described as virtually flat. The metal housing is usually closed in that the edges of the housing cover are welded to the opening edge of the receptacle.
To contact an electrical load located outside the housing, the battery usually comprises at least one contact pole to which the load can be connected. A metal component arranged on an outer side of the housing usually serves as a contact pole.
The battery can comprise two contact poles, of which one (the so-called positive contact pole) connects to the at least one positive electrode via a first pole stud electrically insulated from the metal housing and the other (the so-called negative contact pole) connects to the at least one negative electrode via a second pole stud electrically insulated from the metal housing. However, it is also possible for the metal housing itself to function as a positive or negative contact pole or at least as an electrical bridge between one of the contact poles and the at least one positive or the at least one negative electrode. In this case, the housing has to be electrically connected to the at least one positive electrode or the at least one negative electrode. To this end, an electrical contact between a current conductor belonging to the electrode to be connected and the side of the housing base facing into the housing interior is preferably formed by welding.
In particular, if the battery comprises an individual cell in the form of a winding, this leads to structural problems. Typically, such a winding has a first and a second flat end face and a circumferential casing connecting the two end faces, wherein respective current conductors (so-called “conductor vanes”), via which current can flow from and to the electrodes, exit from the first and the second end face. For obvious reasons, conductor vanes of opposite polarity are spatially separate from one another. Conductor vanes of different polarity preferably also exit at different end faces, for example, conductor vanes connected to the at least one positive electrode at the first end face and conductor vanes connected to the at least one negative electrode at the second end face.
Since the conductor vanes exiting from an end face of such a winding have to be welded to the side of the housing base facing into the housing interior before the winding is inserted into the metal housing, it is necessary either to opt for very long conductor vanes or to extend them by a welded-on conductor. When the winding is inserted into the metal housing following the welding procedure, the conductor vanes or extensions have to be folded and laid against the base. The dead volume inside the metal housing that cannot be used for electrode material is thus increased.
It could therefore be helpful to provide batteries, in particular lithium-ion batteries, having a prismatic metal housing.